void main(List<String> args) {
  List list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10,5,6,7];
  //去重
  List list2 = list.toSet().toList();
  print(list2);
  //排序
  list2.sort((a, b) => a.compareTo(b));
  print(list2);
  list2.sort((a, b) => b.compareTo(a));
  print(list2);
}